On 13 May 2015 at 09:35, Heikki Linnakangas <hlinn...@iki.fi> wrote:
> In summary, the X^1.5 correction seems to work pretty well. It doesn't > completely eliminate the problem, but it makes it a lot better. > Agreed > I don't want to over-compensate for the full-page-write effect either, > because there are also applications where that effect isn't so big. For > example, an application that performs a lot of updates, but all the updates > are on a small number of pages, so the full-page-write storm immediately > after checkpoint doesn't last long. A worst case for this patch would be > such an application - lots of updates on only a few pages - with a long > checkpoint_timeoout but relatively small checkpoint_segments, so that > checkpoints are always driven by checkpoint_segments. I'd like to see some > benchmarking of that worst case before committing anything like this. > We could do better, but that is not a reason not to commit this, as is. Commit, please. This has been in place for a while and still remains: TODO: reduce impact of full page writes -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
